This invention relates to shafts for golf clubs, and, more particularly, to a golf club having a shaft which has a greater outside diameter at the tip and increased torsional stiffness.
Torsional stiffness is a measure of the ability of a golf club to resist twisting about the axis of the shaft. During the golf swing, a torsional force is applied to the shaft as the club head rotates about the shaft axis. More importantly, a twisting about the shaft axis occurs during the impact, if a golf ball is struck off-center, resulting in inaccurate shots. If the grip end of a golf club is clamped in a vise, and a torque of one foot-pound is applied to the club head, the angle of rotation of the club head, measured in degrees, indicates the torsional stiffness. This measurement is sometimes referred to as "torque" in golf club technical specifications.
Flex is another physical characteristic of a golf club. Flex is a measurement of the bending that occurs due to the cantilever loading applied to the club during the golf swing. If the butt end of a golf club is clamped in a vise, and a load of 6.5 pounds is applied at the tip, the deflection of the tip, measured in inches, is a measure of flex.
Both torque and flex affect the performance of a golf club. With respect to torque, more shaft rotation during impact results in more side spin being imparted to the ball. With respect to flex, an optimal stiffness exists for a particular shaft and player.